Currently, to retard the swinging motion and to mitigate the “banging” problem of dipper doors, dipper manufacturers use door brakes and/or retarding mechanisms also known as “snubbers”. These brakes typically comprise a brake assembly installed on the dipper body and connected to the dipper door by a more or less complex linkage assembly.
Examples of dipper door brakes can be found in the following U.S. Pat. Nos. 4,443,957; 4,517,756; 5,613,308; 5,735,067; 5,815,960; 5,974,705; 6,219,946; 6,467,202; 7,096,610.
Typically, failure to have the desired retarding effect on the dipper door will cause an uncontrolled swinging of the dipper door during the opening and closing operation thereof. This uncontrollable swinging will cause repeated impacts between the dipper door and the dipper body, thereby generating excessive noise and subjecting the door to vibrations which will ultimately cause structural damages to the door, to the latching mechanism, and/or to the dipper body.
Though the aforementioned patents propose useful dipper brakes and retarding mechanisms, they generally lack controllability of the braking or retarding. Hence, despite ongoing developments, there is still a need for an improved retarding mechanism for the dipper doors of mining shovel dippers that mitigates at least some of the problems and shortcomings of prior art braking and retarding mechanisms.